Chattanooga, Tenn. (Aug. 15, 2017) – When it comes to breeding some turtles, making even small changes to their environment can be like trying to introduce new foods to an especially picky eater.

“You don’t want to go changing a lot of stuff, or you may unsettle them and have to wait until next year to try again,” says Tennessee Aquarium Senior Herpetologist Bill Hughes. “With some turtle species, it doesn’t matter. With others, you move them to a different space, and they don’t lay eggs for five years. It throws them off track.”

Because of their fickleness and tendency to be slow to reproduce, every successful turtle breeding season is significant, especially for imperiled species. At the Aquarium, Hughes recently celebrated the successful hatching of a pair each of endangered Four-eyed Turtles (Sacalia quadriocellata) and critically endangered Beal’s Four-eyed Turtles (Sacalia bealei).

The hatchlings emerged from their shells in the Aquarium’s rooftop turtle nursery on June 13 (Four-eyed) and July 2-3 (Beal’s) from eggs that had been incubating at 82 degrees since being laid in April.

The Aquarium is home to the largest collection of freshwater turtles in North America. In 2007, it received national attention as the first North American zoo or aquarium to successfully hatch a Beal’s Four-eyed Turtle.

In the last decade, the Aquarium has had continued success in hatching these “four-eyed” species, which are native to Southeast Asia and named due to eye-like markings on the top of their heads. Including the most recent babies, the Aquarium has successfully hatched 15 Beal’s Four-eyed and 37 Four-eyed Turtles since 2007.

In all, just 47 Four-eyed and 24 Beal’s Four-eyed are housed in North American facilities accredited by the Association of Zoos and Aquariums (AZA). Hatchlings raised at the Tennessee Aquarium have been shared with other caretakers in an effort to shore up their captive population. In 2015, a trio of Beal’s Four-eyed were sent to the Knoxville Zoo — the only other AZA institution to house them — and Four-eyed hatchlings have been shipped to facilities as far as New York, Texas and California.

In light of these turtles’ limited numbers, both in the wild and in captivity, Hughes says he’s largely opted to avoid tampering with his breeding setup for fear of derailing programs that are helping to significantly bolster their overall populations.

“The only thing I’ve really changed is cooling them off more in winter and incubating them a degree or two warmer,” he explains. “They’re all still in their same space they’ve been in for years, which is helping.”

Like many Southeast Asian species, both the Beal’s Four-eyed and Four-eyed Turtle wild populations have been in free fall in recent decades. This decline is thanks to a combination of human-induced threats, including habitat destruction and capture for use as a food source or to supply the pet trade.

According to a 2014 study by the International Union for Conservation of Nature, 50-60 percent of the 335 modern turtle and tortoise species are either extinct or threatened with extinction. That gives them the dubious distinction as the most imperiled major group of vertebrates on the planet.

The Aquarium’s successful rearing of Beal’s Four-eyed and Four-eyed Turtles is crucial to their survivability. Hughes serves as the coordinator of the Species Survival Plan (SSP) for the Four-eyed Turtle since that plan became active in 2012. This year, the Beal’s Four-eyed Turtle became a candidate for the program, and Hughes says the turtle’s conservation status puts it on the fast track to achieving full SSP status in the future.

Even after years of success in raising them, Hughes never tires of seeing new turtles emerge from their eggs. And as you would expect from such dogged creatures of habit, they tend to arrive almost like clockwork, he says.

“They lay at the same time or year, and the eggs hatch at the same time of year, so it’s like a floating holiday that doesn’t float that much. You know when it’s coming,” Hughes says. “It’s still a thrill to see them.”